1. Field of the Invention
The present invention relates to an observation apparatus for observing or photographing an object image at a predetermined magnification and, more particularly, to an infinity objective system capable of observing a target sample surface at a very low magnification in a wide field of view. Note that the very low magnification means a magnification of about 1.5xc3x97 or less in the present invention.
2. Related Background Art
In general, an interchangeable objective mounted on the revolver of a microscope must be designed such that its total length falls within the parfocal distance for the objective (distance along the optical axis between a stage surface for mounting a sample and the reference plane of the revolver used when the objective is mounted on the revolver).
If, therefore, an objective for a very low magnification of, e.g., 1xc3x97 or less is to be designed, a required focal length increases, and it becomes difficult to make the total length fall within the parfocal distance for the objective. As a result, a conventional microscope has no objective for a very low magnification of 1xc3x97 or less and attachable to a revolver.
As described above, when a wide-range image of the target sample surface is to be observed or photographed, a conventional microscope cannot meet this demand. This case is coped with by using apparatuses such as a stereomicroscope and a macro camera, other than a microscope. Therefore, it is necessary to use a microscope when the details of a sample are observed or photographed, and a stereomicroscope or a macro camera when the entire sample is observed or photographed. As a result, an observer must perform many cumbersome operations such as positioning of a sample each time an apparatus to be used is changed, resulting in a very low working efficiency.
It is an object of the present invention to provide an observation apparatus with an objective system which allows observation or photography of a sample in a wide range from a high magnification which can be realized by a normal microscope to a very low magnification which cannot be realized by the normal microscope. Therefore, the observation apparatus according to the present invention comprises a basic structure as a normal microscope with an objective system constituted by an interchangeable objective unit attached to a revolver and a tube lens unit fixed at a position to which a light beam is guided from the objective unit. Particularly, the observation apparatus according to the present invention comprises a mechanism capable of setting a special optical system (auxiliary lens unit) constituting part of the objective unit on the optical axis of the objective system between the revolver and the tube lens unit. A partial objective unit constituting part of the objective unit is attached to the revolver to constitute the objective unit for a very low magnification by the partial objective unit and the auxiliary lens unit. In this manner, the objective unit whose total length is larger than the parfocal distance for the objective in this apparatus can be constituted.
With the above arrangement, the objective system in the observation apparatus according to the present invention comprises an arrangement (first aspect) realized by the partial objective unit attached to the revolver, the auxiliary lens unit (the partial objective unit and the auxiliary lens unit constitute the objective unit for a very low magnification), and the tube lens unit fixed at a predetermined position so as to realize observation or photography at a very low magnification, and an arrangement (second aspect) realized by the objective and tube lens units for microscopic observation.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.